Method for Transmitting and Receiving Frame

1. A method of transmitting a frame by a device in a wireless communication network, the method comprising: generating a High Efficiency signal A (HE-SIG-A) field including a symbol having a first subcarrier spacing, the HE-SIG-A field carrying common signaling information for a plurality of receiving devices, the HE-SIG-A field occupying a 20 MHz bandwidth; generating a High Efficiency signal B (HE-SIG-B) field carrying HE-SIG-B information, the HE-SIG-B information including dedicated signaling information for each of the plurality of receiving devices, and the HE-SIG-B field occupying the 20 MHz bandwidth; generating a data field including a symbol having a second subcarrier spacing narrower than the first subcarrier spacing, the data field carrying data for the plurality of receiving devices; and transmitting a frame including the HE-SIG-A field, the HE-SIG-B field, and the data field, wherein an upper 10 MHz of the 20 MHz bandwidth in the HE-SIG-B field carries the HE-SIG-B information, and a lower 10 MHz of the 20 MHz bandwidth in the HE-SIG-B carries a duplicate of the HE-SIG-B information carried in the upper 10 MHz of the 20 MHz bandwidth in the HE-SIG-B field.

2. The method of claim 1 , wherein the second subcarrier spacing is ¼ of the first subcarrier spacing.

3. The method of claim 1 , wherein a Fast Fourier Transform (FFT) period of the symbol having the second subcarrier spacing is four times of an FFT period of the symbol having the first subcarrier spacing.

4. The method of claim 1 , further comprising generating a long training field following the HE-SIG-A field and used for channel estimation, wherein the long training field includes another symbol having the second subcarrier spacing.

5. The method of claim 1 , wherein an entire bandwidth is divided in to a plurality of 20 MHz channels, wherein the HE-SIG-A field is duplicated and transmitted on the plurality of 20 MHz channels, and wherein the entire bandwidth is divided into a plurality of resource blocks for a plurality of users in the data field, and a bandwidth narrower than 20 MHz is allowed for one or more of the plurality of resource blocks.

6. The method of claim 5 , further comprising a legacy preamble preceding the HE-SIG-A field and being compatible with a previous version wireless communication network, wherein the legacy preamble includes a legacy short training field, a legacy long training field, and a legacy signal field, and wherein the legacy short training field, the legacy long training field, and the legacy signal field are duplicated and transmitted on the plurality of 20 MHz channels.

7. The method of claim 1 , further comprising selecting a guard interval of guard intervals for the symbol having the second subcarrier spacing out of a set of allowable guard intervals for the symbol having the second subcarrier spacing according to a user or according to a current condition of a channel.

8. The method of claim 7 , wherein the set of allowable guard interval durations for the symbol having the second subcarrier spacing includes 0.8 μs, 1.6 μs, and 3.2 μs.

9. A method of transmitting a frame by a device in a wireless communication network, the method comprising: transmitting, on a 20 MHz channel, a legacy preamble compatible with a previous version wireless communication network; transmitting, on the 20 MHz channel, a High Efficiency signal A (HE-SIG-A) field carrying common signaling information for a plurality of receiving devices; transmitting, on the 20 MHz channel, a HE-SIG-B field carrying HE-SIG-B information, the HE-SIG-B information including dedicated signaling information for each of the plurality of receiving devices; and transmitting a data field for the plurality of receiving devices, wherein an upper 10 MHz of the 20 MHz channel in the HE-SIG-B field carries the HE-SIG-B information, and a lower 10 MHz of the 20 MHz channel in the HE-SIG-B carries a duplicate of the HE-SIG-B information carried in the upper 10 MHz of the 20 MHz channel in the HE-SIG-B field.

10. The method of claim 9 , further comprising: transmitting a long training field following the signal field and used for channel estimation.

11. The method of claim 9 , wherein the legacy preamble further includes a legacy short training field used for an automatic gain control.

12. The method of claim 9 , wherein a symbol of the legacy preamble and a symbol of the HE-SIG-A field have a same subcarrier spacing.

13. The method of claim 9 , wherein subcarrier spacing of a symbol of the HE-SIG-A field is narrower than subcarrier spacing of a symbol of the legacy preamble.

14. The method of claim 13 , wherein a first Fast Fourier Transform (FFT) is used in the legacy preamble and a second FFT having a larger size than the first FFT is used in the data field.

15. The method of claim 13 , further comprising allocating pilots to the data field to allow a phase tracking to be performed by a symbol period unit including a plurality of consecutive symbols.

16. The method of claim 9 , further comprising selecting a guard interval of guard intervals for a symbol of the data field out of a set of allowable guard intervals for the symbol of the data field according to a user or according to a current condition of a channel.

17. A method of receiving a frame by a device in a wireless communication network, the method comprising: receiving a High Efficiency signal A (HE-SIG-A) field including a symbol having a first subcarrier spacing, the HE-SIG-A field carrying signaling information for a plurality of receiving devices including the device, the HE-SIG-A field occupying a 20 MHz bandwidth; decoding a symbol of the HE-SIG-A field on a basis of the first subcarrier spacing; receiving a High Efficiency signal B (HE-SIG-B) field carrying HE-SIG-B information, the HE-SIG-B information including dedicated signaling information for each of the plurality of receiving devices, and the HE-SIG-B field occupying the 20 MHz bandwidth; decoding the High Efficiency signal B (HE-SIG-B) field; receiving a data field including a symbol having a second subcarrier spacing narrower than the first subcarrier spacing, the data field carrying data; and decoding the symbol of the data field on a basis of the second subcarrier spacing, wherein an upper 10 MHz of the 20 MHz bandwidth in the HE-SIG-B field carries the HE-SIG-B information, and a lower 10 MHz of the 20 MHz bandwidth in the HE-SIG-B carries a duplicate of the HE-SIG-B information carried in the upper 10 MHz of the 20 MHz bandwidth in the HE-SIG-B field.

18. The method of claim 17 , wherein the second subcarrier spacing is ¼ of the first subcarrier spacing.

19. The method of claim 17 , wherein a Fast Fourier Transform (FFT) period of the symbol having the second subcarrier spacing is four times of an FFT period of the symbol having the first subcarrier spacing.

20. The method of claim 17 , wherein receiving the data field includes: receiving a resource unit on a first subband that is assigned to the device among a plurality of subbands into which the 20 MHz bandwidth is divided, and wherein a second subband among the plurality of subbands into which the 20 MHz bandwidth is divided is assigned to another device different from the device.

21. The method of claim 17 , further comprising performing a phase tracking by extracting pilots by a symbol period unit including a plurality of consecutive symbols.